- a stay, or line, extending forward from the mainmast, supporting it and holding it in position
- a chief support
The definition of a mainstay is something that is depended on, or something that is necessary.
Fruits and vegetables are an example of the mainstay of a healthy diet.
- A chief support: Agriculture is a mainstay of the economy.
- Nautical A stay running forward from the mainmast to the deck of a sailing vessel.
- Fishing is the occupation of the men, and the real mainstay of the inhabitants.
- That this doctrine was a mainstay of Jewish faith in those very days of exile which gave the Sabbath a new importance for the faithful.
- The mainstay of the agriculture of the department is the raising of live-stock, especially of cattle of the Aubrac breed, for which Laguiole is an important market.
- It is therefore the mainstay of the scholar in investigating or restoring the word~ forms of the ancient language.
- The deserters from Cicala's army, distributed in armed bands throughout Asia Minor, had become centres round which all the elements of discontent gathered, and formed the mainstay of the Jellali sectaries who, at this time, rose in insurrection and ravaged Anatolia.